FIG. 15 illustrates an example of a reforming liquid producing device of the related art. A reforming liquid producing device, in which first electrode 801 and second electrode 802 are disposed in liquid 803 (for example, water), a high voltage pulse is applied between both electrodes 801 and 802 from pulse power supply 804 to evaporate liquid 803 and generate plasma 805, thereby producing a reforming liquid containing a component having, for example, oxidizing power such as a hydroxyl radical (OH radical) or hydrogen peroxide, is known. Particularly, it is known that the OH radical has high oxidizing power and a high sterilizing operation and is provided by mixing the reforming liquid containing these components. The OH radical has a high sterilizing operation with respect to, for example, bacteria. In addition, it is known that when plasma 805 is covered by liquid 803 a liquid-derived component is easily generated by generating plasma 805 in liquid 803. For example, it is known that the OH radical or hydrogen peroxide is easily produced by generating plasma 805 in water.
However, in a case of the reforming liquid producing device of the related art, not only is a high applying voltage required for evaporating liquid 803 but also the generation efficiency of plasma 805 is low. There is also a problem that it takes a long period of time to reform liquid 803.
Therefore, a reforming liquid producing device, in which gas introduced from an outside is interposed between both electrodes to improve the generation efficiency of plasma while lowering the applying voltage, is known (see Japanese Patent No. 4041224). In the reforming liquid producing device (FIG. 16) disclosed in Japanese Patent No. 4041224, gas 904 (for example, oxygen) is interposed between anode electrode 901 and cathode electrode 902 together with processed liquid 903, and a pulse voltage is applied between both electrodes 901 and 902. Plasma is generated in gas 904 and reformation of processed liquid 903 is generated on a contact surface between the plasma and the processed liquid 903 by applying the pulse voltage. According to the reforming liquid producing device disclosed in Japanese Patent No. 4041224, it is possible to reduce the applying voltage and to perform reformation of processed liquid 903 by efficiently generating plasma as compared to a case where gas is not interposed.